Question

A right isosceles triangle of side $a$ has charges $q,+2q$ and $-q$ arranged on its vertices, as shown. What does the sign of $U$ signify?

• A. The negative sign means that work was done on the agent who assembled these charges in moving them in from infinity.
• B. The positive sign means that work was done on the agent who assembled these charges in moving them in from infinity.
• C. The negative sign means that work was done by the agent who assembled these charges in moving them in from infinity.
• D. The positive sign means that work was done by the agent who assembled these charges in moving them in from infinity.

Answer 1

Answer: (C)

The negative sign means that work was done by the agent who assembled these charges in moving them in from infinity.

The negative sign means that work done by the agent who assembled there charges in moving them in from infinity.

In a right isosceles triangles three possible arrangements of charge $S$ are possible.

1) $+q$ at right angle, rest at other vertices.

2) $-q$ at right angle, rest at other vertices.

3) $+2q$ at right angle, rest at other vertices.